Safety mechanism for use in connection with presses and other apparatuses such as conventional metal bending and forming apparatuses



Sept. 2, 1969 J, LINDQUIST ET AL 3,464,291

SAFETY MECHANISM FOR USE IN CONNECTION WITH PRESSES AND OTHER APPARATUSES sucn AS CONVENTIONAL METAL BENDING AND FORMING APPARATUSES Filed Dec. 22, 1967 4 Sheets-Sheet 1 IN VENI'ORS. Jan/As" fizazme x/l/zaz/zsz'i .B ZERY A STUA/KEL B) aiwwui Q. Q'I'K A:

3,464,291 SAFETY MECHANISM FOR USE IN CONNECTION WITH PRESSES AND Sept. 2, 1969 J. T. LINDQUIST ET AL OTHER APPARATUSES SUCH AS CONVENTIONAL METAL BENDING AND FORMING APPARATUSES 4 Sheets-Sheet 2 Filed Dec. 22. 1967 INVENTORS- T Q I mu m may .5 LA X w mm E Sept. 2, 1969 J. T. LINDQUIST ET AL 3,464,291

SAFETY MECHANISM F011 USE IN CONNECTION WITH PRESSES AND i OTHER APPARATUSES SUCH AS CONVENTIONAL METAL BENDING AND FORMING APPARATUSES Filed Dec. 22, 1967 4 Sheets-Sheet 5 AIR LINE mvsm'oxs (fa/ms THEOEORE j/Z/VDQll/Sf .BAR 2r 4' firm/ HZ BY Exiwwwb 8/. 3

.ZWEJK 47mm N5 4 Sept. 2, 1969 J. T. LINDQUIST ET AL 3,464,291

SAFETY MECHANISM FOR USE IN CONNECTION WITH PRESSES AND OTHER APPARATUSES SUCH AS CONVENTIONAL METAL BENDING AND FORMING APPARATUSES Filed Dec. 22, 1967 4 Sheets-Sheet 4 FRO AIRS PP Him TO M U L Y 95 CLUTCH v INVENTORS.

(fa/ms Zyfozoxzfiz vgaaisri F 9 8 BARRY A-LS'JZL VKE B gdwwwl. 6.

THEIR ATTOXJVEX United States Patent US. 'Cl. 74--613 6 Claims ABSTRACT OF THE DISCLOSURE A safety mechanism having a guard plate for guarding the work area of a metal forming press to provide maximum protection against both accidental and unintentional press operation when the operator is feeding the workpiece into the work area and when the ram with its punch is in its downward work stroke. When the guard plate is in raised position, the press is rendered inoperative until the guard plate is dropped to guard position, in which position it cooperates with electrical components which render the press operative if the guard plate is in its proper down position; otherwise if the guard plate is not in its fully dropped position, the press cannot be operated.

Summary of the invention An object of this invention is to provide a guard plate which is mechanically and electrically interlocked with the press operating components so that any failure in the mechanical, electrical or pneumatic components renders the press inoperative, at which time the operator becomes aware that the guard plate is not functioning properly and the press cannot be operated until the malfunction has been corrected.

The invention will be best understood by reference to the accompanying drawings showing the preferred form of construction, and in which:

FIG. 1 is a perspective view of a conventional apparatus with which the invention is adapted to be associated, in which view the ram of the apparatus is shown in its upper position and the guard plate in its down position;

FIG. 2 is a fragmentary sectional detail view of the guard-actuating mechanism embodying the invention, with the guard plate in its elevated position;

FIG. 3 is a fragmentary sectional detail view similar to that shown in FIG. 2, but with the guard plate in its down position obstructing the work area of the press;

FIG. 4 is a fragmentary sectional detail view taken substantially on line 44 of FIG. 2;

FIG. 5 is a fragmentary elevational view of a power take-off assembly embodied in the invention;

FIG. 6 is a fragmentary sectional elevational view of a control panel embodied in the invention;

FIG. 7 is a schematic diagram of a preferred embodiment of a circuit employed in the invention;

FIG. 8 is a schematic diagram of the air system embodied in this invention.

This invention constitues an improvement over that shown in United States Letters Patent No. 3,269,215, granted to Jonas Theodore Lindquist on Aug. 30, 1966, on a Safety Mechanism.

FIG. 1 of the drawings exemplifies a conventional press for bending and forming material. Only so much of the press is illustrated as will enable one skilled in the art to understand the invention. In this connection, the press is indicated generally at P. It includes a ram R operable in the usual and conventional manner by mech- 3,464,291 Patented Sept. 2, 1969 ICC anism indicated at M, which mechanism embodies no part of the present invention.

The press further includes a die base D which supports the die which cooperates with the ram R and its die to form or shape the work. It is with presses of this character, as well as others, that the guard G and its associated mechanism is associated. Such guard G is substantially of the construction of the guard shown in Patent No. 3,269,215.

The guard G when released in a manner presently described drops into the work area by gravity and is elevated by pneumatic means, the latter electrically controlled.

The guard as illustrated in FIGS. 2 and 3 and as shown on the press in FIG. 1, comprises two elongated transparent sheets 10 hingedly connected together as at 11 along their opposite longitudinally extending edges. The upper of the two sheets 10 is fixedly connected in any suitable manner as at 12 to the lower end portions of vertically extending rods 13. The upper end portions of these rods 13 extend through elongated tubular members '14 carried by the bottom wall 15 of a housing 16. The upper end portion of each rod 13 is connected as at 17 to corresponding end portions of leaf springs 18 which project upwardly through a sleeve 19 with their opposite end portions coiled upon themselves and fixedly secured to pins 20 within an enclosure 21 carried by the housing 16 as shown in FIG. 2.

The upper end portions of each of the rods 13 have fixed thereto a substantially Z-shaped plate 22 providing spaced horizontally extending portions 23 and 24. The plate 22 carries a dashpot 25 which cooperates with a tapered pin 26 carried by the bottom wall 15 and which under proper conditions will enter a socket 27 of the dashpot 25. The purpose and function of the pin 26 and dashpot 25 is to cooperate with the springs 18 to cushion the drop of the guard G as it is dropped by gravity in a manner hereinafter set forth.

Within the housing 16 is an adjustable plate 29 pivoted by a pin 30 to a plate 31 fixedly connected to the back wall 28.

To the plate 29 is pivoted as at 32 a latch arm 33 which has a latchhead 34 adapted to have latched engagement with a latch pin 35 under conditions to be hereinafter explained. The latch pin 35 is carried by an arm 36. The latch pin 35 projects into the bifurcated end portion 37 of an arm 38 which extends in a direction opposite to the arm 36, and which arm 38 is fixedly connected to an arm 41'.

An arm 41 is pivoted as at 42 to one end of a connecting link 44, the opposite end of the connecting link 44 being pivotally connected as at 45 to a link 46 pivoted by means of a pin 45 to a plate 49 fixed to the back wall 28 of the casing 16.

The arm 41 is pivoted as at 41 to a plate 49' fixed to the back wall 28 and as at 42' to a connecting plate 43 which is also pivoted as at 42" to a link 46'. The link 46 is in turn pivoted as at 48 to a plate 48' fixed to the back wall of the housing 16. Fixedly connected to each of the links 46 and 46 is a lift arm 47.

The outer end portion 50 of each of the arms 47 engages beneath the horizontally extending portion 24 of the plates 22 for reasons hereinafter explained.

Secured within the housing 16 adjacent each of the end walls 16' thereof, is a snap-action switch 51. Each switch includes a plunger 52 which is disposed in the path of the horizontal extension 23 of the Z-shaped plate 22 for reasons hereinafter set forth.

Each switch 51 includes a pair of contacts 89 and 89' alternately engageable by a switch blade of the switch 51 in a manner hereinafter explained.

The latch arm 33 is pivotally connected as at 53 to a link 54 which in turn is pivotally connected as at 55 to the plunger 56 of an electromagnetic solenoid 57 of a known construction. The solenoid 57 is connected as at 57' to and movable with the adjustable plate 29 in a manner hereinafter described.

Pivotally connected to the arm 36 intermediate its opposite end portions as 58, is an arm 59 which provides at its lower end portion a lateral extension 60 on which is secured a feed nut 61.

Threaded into this nut 61 is the end portion 62 of a threaded shaft 63 which extends through a sleeve 64 secured to a boss 65 carried by the bottom wall 15. The lower end of the shaft 63 carries a finger wheel 65' by means of which the shaft 63 is rotated.

By rotating the shaft 63 the plate 29 is adjusted relative to its pivot pin 40, with the result that the position of the latchhead 34 and latch pin 35 is varied to adjust the distance that the guard plate is dropped into the work area of the press.

Connected as at 66 is the end of a plunger 67 of an air cylinder 68 secured to and carried by the housing 16 through the medium of a mounting bracket 69. The air cylinder 68 has communication with an electromagnetic solenoid valve 70 which in turn has connection with an air line 71 and is actuated in a manner hereinafter described, to admit air into the cylinder 68 to project the plunger 67 in a direction to effect lifting of the guard plate through the medium of the lift arms 47. In elevated position the arms are held in such position by the latch arm 33 and pin 35.

The mechanism thus described is mounted as shown in the housing 16. This housing 16 is secured to the frame of the press by means of a shaft 72 (FIG. 4). The ends of this shaft 72 are secured in pinch bearings 73 (FIG. 4) secured to the housing as at 74, the shaft 72 being mounted in suitable bearings (not shown) provided by the frame of the press. To adjust the housing 16 so as to bring the guard G vertically closer to the work area, the operator adjusts a thumb shaft 75 which loosens the bearings 73 to the extent that the operator may tilt the housing 16 in the desired direction so as to dispose the guard closer or farther away from its position with respect to the press at the work area.

In FIGS. and 6 we have illustrated certain of the electrical components essential to a proper operation of the safety mechanism and the ram of the press. These components will be best understood from the description now to follow with respect to the electrical circuits involved. Such circuits are shown in FIGS. 7 and 8.

In FIG. 7 the various switches and other electrical components are in normal rest position with the guard plate elevated and the ram of the press at rest. The circuit now to be described is preferably referred to as the latch release circuit for it is this circuit which effects the release of the guard G to permit the same to drop by gravity into the work area of the press.

In this circuit are employed switches 51 connected in series, and each comprising a switch blade adapted to alternately engage contacts 89 and 89'. There are also in this circuit normally closed switches 83 and 83 connected in series as well as a pair of switches 84 and 84' connected in series and each including a switch blade adapted to alternately engage contacts C1 and C2.

The latch release circuit also includes a manually operated starting switch 81 actuated by a pneumatically operated plunger 80, which plunger is operated in a manner presently explained.

The latch release circuit may be traced as follows:

From power line P through switch 81, when closed, line A, through closed relay switch 82, through line B, through normally closed switches 83' and 83, through switches 84 and 84' conditioned with their respective switch blades in engagement with contacts C1. From contacts C1 the circuit continues through line C through 4 normally closed switches 51 through line D, solenoid 57, line B, to power line P.

When the latch release circuit is energized by the closing of switch 81 the solenoid 57 pivots the arm 33 to disengage the latch head 34 from the latch pin 35 whereupon the guard plate by gravity will drop into the work area of the press before the ram starts to move. The guard plate is shown in such position in FIG. 1.

When in such area the guard plate conditions switches 51 with their blades in contact with contacts 89'. In such condition the release solenoid 57 is deenergized and an initial energizing circuit established in the following manner for electromagnetic solenoids 92 and 93 to open valves 94 and 95 of the air line to the cylinder for moving the clutch rod 95' to actuate the clutch (not shown) of the press to move the ram R.

The closing of the start switch 81 also establishes an initial energizing circuit for relay 87 which may be traced from power line P through closed start switch 81, line A through normally closed switch 82, line B to line B, relay 87 to power line P.

The initial energization of relay 87 closes normally open switch 88 and normally open switch 90 thus establishing the initial energizing circuit for solenoids 92 and 93.

The closing of the switch 90 establishes a holding circuit for relay 87 and a circuit for relay 96. The holding circuit for relay 87 may be traced from power line P through switches 84 and 84' with their switch blades conditioned to contact contacts C2. From contacts C2 the circuit continues through line G, closed switch 90, line F, line B to line B through relay 87 to power line P".

The circuit for energizing the relay 96 may be traced from power line P to switches 84 and 84' when conditioned with their switch blades in contact with contacts C2, line G, line H, to relay 96 and thence to power line P".

Energization of the relay 96 closes normally open switch 97 which takes over the function of the start switch 81 when it opens.

Relay 101 when energized closes switches 102 and 102. Relay 101 is energized by a circuit which may be traced from power line P, switch 100, closed in a manner hereinafter stated, line K, relay 101 to power line P".

When switches 97, 102, 102 and 88 are closed a holding circuit for the solenoids 92 and 93 is established to hold these solenoids energized when the switch blades of switches 51 are repositioned to again engage the contacts 89 instead of 89, which occurs when the guard plate initiates its return movement from the work area. This holding circuit may be traced thus:

From power line P' through switches 97, 102, 102', line I, switch 88, line I, solenoids 92 and 93 to power line P".

The switches 102 and 102' in the solenoid holding circuit are held closed by the relay 101. The circuit for relay 101 is traced from power line P' through switch 97, switch 102, line K, relay 101 to power line P".

Upon completion of the forming of the work the ram moves the cam 97 (FIG. 5) from engagement with the roller 99 whereupon the switch 100 will open. When the ram returns to its starting position the cam 97 is moved into engagement with the roller 98 whereupon switches 84 and 84' will be conditioned with their blades in engagement with contacts C1. This change in the condition of switches 84 and 84' will deenergize the relays 96, 101 and 87 resulting in the opening of the switch 88 deenergizing the main and auxiliary solenoids 92 and 93, closing the switch 82 and opening of switches 102 and 102' and 97. The lift solenoid 70 will also be deenergized at which time the guard will have been latched in its raised position from the work area by the latch arm 33 (FIG. 1). The circuit is now conditioned as shown in FIG. 7 for a repeat operation.

In the power lines P and P are arranged normally open switches 76 which must be closed when the circuit is operative.

The cam 97 comprises a plate a having an elongated slot b which receives a head-bearing stud bolt carried by a plate d. The plates d and a can be adjusted relative to each other and fixed in such adjusted position by a tightening of the stud bolt 0. The cam 97' is pivotally carried by a shaft e journaled in the housing 1 (FIG. 5) and in turn carried by an arm g, which is connected as at h to a link i fixed as at k to the ram R. The arrangement is such that movement of the ram R effects pivotal movement of the cam 97.

The parts a and d of the cam 97 may be adjusted rela tive to each other such that the cam 97' will move ofi the roller 98 as the ram starts its down movement toward the work, and will engage the roller 99 just as the ram touches the work and thereby close the switch 100 to energize the lift solenoid 70 to retract the guard plate after the ram has formed the work.

The switch 100 may be adjusted relative to the cam 97' through the medium of the thread-bearing rod 1 adjustably threaded through a 'lug m carried by the casing 1. The rod 1 has a thumbwheel n attached to its exterior and to facilitate adjusting of the switch 100. The rod 1 is fixed in an adjusted position by a thumb bolt p (FIG. 5).

Should either of the solenoids 92 or 93 fail to the extent that the switches 83 or 83 do not close, then in that case the latch release solenoid 57 will not be energized because of an incomplete circuit. In such case the guard plate G will not drop to its down position with respect to the work area, and a circuit will not be established to the main or auxiliary solenoids 92 and *93 and the latter will not open the air valve 94 or 95 with the result that the ram of the press will remain in its upper starting position.

The components herein described and as shown in FIG. 6 are in practice enclosed in a suitable housing H, atached to the press P in any suitable manner and location.

Summary of operation When the press is at rest the guard plate G is in its initially elevated position with respect to the work area and the ram of the press P is in its starting position. The guard plate G is released for movement by gravity into the work area by the closing of the start switch 81 through the medium of the manual actuation of the air foot valve 77' (FIG. 8) which admits compressed air to the cylinder 78, to project the plunger 80 in a direction to close the start switch 81.

The closing of the start switch 81 in the latch release circuit hereinbefore described results in the energization of the latch release solenoid 57 which releasing the guard plate permitting the same to drop by gravity into the work area so as to prevent the operator from inserting any part of his body into that area. At the termination of the dropping of the guard plate G into the work area the main and auxiliary solenoids 92 and 93 are energized in the manner hereinbefore described.

The energization of the solenoids 92 and 93 results in the opening of the air valves 94 and 95, allowing compressed air to flow into the cylinder 96' to operate the clutch rod 95' which controls the clutch (not shown) which effects the movement of the ram R through its cycle of operation.

A holding circuit is set up for the main and auxiliary solenoids 92 and 93 in a manner hereinbefore described. This holding circuit remains eifective until the ram R has completed one cycle of operation. As the ram R moves from its initial starting position downwardly in a direction toward the work, it moves the cam 97' (FIG. 5) off the roller 98 to condition the switches 84 and 84' with their switch blades engaging the contacts C2, thus to hold energized the relay coils 87, 101 and 96 to establish the hereinbefore referred to holding circuit for the main and auxiliary solenoids 92 and 93.

This holding circuit for solenoids 92 and 93 is effective until the ram at the end of its cycle of operation reengages the roller 98 at which time the switch blades of switch 84-84 are moved from engagement with contacts C2 into engagement with contacts C1 for reasons hereinbefore explained.

When the ram R is in its down position and has operated upon the work, the cam 97' will have engaged the roller 99 to close the switch 100. Closing of this switch 100 energizes the electromagnetic coil 70 to open the air valve 70' to permit compressed air to enter the cylinder '68 to project the plunger 67 in a direction to cause the guard lifting mechanism (FIGS. 2 and 3) to elevate the guard plate G to its original starting position, at which time the ram R will have returned to its original starting position ready for a repeat operation.

The guard plate is in its down position with respect to the work area before the ram of the press operates. Such ram cannot operate until such guard plate is in such position.

By adjustment of the plate 29 (FIGS. 2 and 3) the lower edge of the guard plate when the latter is in down position will be just above the die of the press, a sufiicient distance to permit the operator to insert only the work upon the die. Any interference with the complete drop of the guard plate to such distance, whether by the hand or any part thereof of the operator, will render the press incapable of operation due to the fact that the guard plate cannot engage the plungers 52 of the switches 51 to actuate the latter.

The arrangement is such that just as the ram touches the work the guard plate retracts so that it is raised above the work being formed in time so as not to be in the way of such work. By the time that the ram has fully formed the work piece the guard plate will have been fully retracted. Subsequent operation of the press cannot again take place without the guard plate first having gravitated into down position just above the work before the ram starts its down movement.

The switches and solenoids herein referred to are of a well-known commercial construction and, therefore, will not be described or shown in detail.

The foregoing sequence of operation of the electric circuit and its component parts results in a press of the character herein described which has the maximum degree of safety in its operation, guarding against accidents which might result in injury to the operator of the press.

While we have illustrated and described the preferred form of construction for carrying our invention into effect, this is capable of variation and modification without departing from the spirit of the invention. We, therefore, do not wish to be limited to the precise details of construction set forth, but desire to avail ourselves of such variations and modifications as come within the scope of the appended claims.

Having thus described our invention, what we claim as new and desire to protect by Letters Patent is:

1. An improvement in a safety device for a metal forming press having a work area wherein work to be formed is placed, a ram movable into said area for forming said work and including a clutch operating rod a guard plate (G) movable into and out of said work area, means (33, 35, 37, 38) for releasably holding the guard plate clear of the work area, a releasing solenoid (57) for actuating said holding means (33, 35, 37, 38) to release the guard plate for movement by gravity into said work area before said ram has moved into said are a, the improvement comprising:

(a) means (96') for moving said rod (95') in a direction to effect movement of said ram,

(b) electromagnetic means (92-93) for controlling said rod moving means (96), (c) an electric circuit (J) having a power source 7 (P'-P") for said electromagnetic means (92-93),

((1) an electric circuit (A, B, C, D, E) having a power source for said releasing solenoid (57 (e) switch means (81) in said releasing solenoid circuit (A to E) to initiate energization of said releas ing solenoid circuit (A to E),

(f) a holding circuit (J, 1') including relay actuated switches (88, 102, 102, 97) for holding said electromagnetic means circuit (J) energized upon opening of said manually operated switch means (81),

(g) an electric circuit (6, H, J, K) for actuating the relays (96, 87, 101) of said relay actuated switches (88, 1'02, 102', 97) in said holding circuit (J, I),

(h) switch means (51) in said releasing solenoid circuit (A to E) and said holding circuit (J, J) and actuated by engagement with the guard plate (G) when in said work area to deenergize the releasing solenoid circuit (A to E), and to energize said electromagnetic means (92-93) controlling the rod moving means (96'),

(i) switch means (100) actuated by the ram after the ram has formed the work for deenergizing said holding circuit (J, J) and (j) means (68, 70, 70') for moving said guard plate (G) from said work area when said ram engages said work.

2. The improvement in a safety device for a metal forming press as defined in claim 1 wherein the switch means in said releasing solenoid circuit (A to E) is a momentarily manually closed switch (81).

3. The improvement in a safety device for a metal forming press as defined in claim 1 wherein the means for moving said guard plate (G) from said work area includes pneumatically operated means (68, 70,

4. The improvement in a safety device for a metal forming press as defined in claim 3 wherein there is provided an electromagnetic solenoid (70) for controlling operation of the pneumatically actuated means (68, 70') for moving said guard plate from said work area.

5. The improvement in a safety device for a metal forming press as defined in claim 1 wherein the means (96) for moving said clutch rod is pneumatically actuated, and the control means (92-93) is electromagnetic valves.

6. The improvement in a safety device for a metal forming press as defined by claim 5, characterized by the inclusion of switch means (83-83) for deenergizing said releasing solenoid circuit (A to E) actuated by said electromagnetic control means (92-93).

References Cited UNITED STATES PATENTS 1,191,042 7/1916 Sunday 74-615 1,204,473 11/1916 Moore 74615 1,270,578 6/1918 Winters et a1. 74-616 3,213,992. 10/1965 Gustafson et al. 192-434 FRED C. MATTERN, 1a., Primary Examiner F. D. SHOEMAKER, Assistant Examiner US. Cl. X.R. 

